Data carrier having identifiers

ABSTRACT

The invention relates to a data carrier into which, by means of a laser beam, identifiers are introduced that are visible in the form of irreversible changes, caused by the laser beam, in the optical properties of the data carrier. According to the present invention, the data carrier comprises a laser-sensitive layer ( 20 ) that is opaque in the visible spectral range, and that is combined with a securing layer ( 22 ) that is metallized at least in a sub-area, the identifiers ( 30, 32 ) being introduced by the laser beam simultaneously and in perfect register into the laser-sensitive layer ( 20 ) and the metallized sub-area ( 24 ) of the securing layer ( 22 ).

The invention relates to a data carrier into which, by means of a laserbeam, identifiers are introduced that are visible in the form ofirreversible changes, caused by the laser beam, in the opticalproperties of the data carrier. The present invention further relates toa method for manufacturing such a data carrier, as well as a method forchecking the integrity of such data carriers.

It is known to personalize identification cards, such as credit cards,bank cards or identity cards, by means of laser engraving. Inpersonalization by laser engraving, the optical properties of the cardmaterial are irreversibly changed, in the form of a desired identifier,through suitable guidance of a laser beam.

For example, the identification card described in publication DE 29 07004 includes two cover sheets and a card insert in which, through one ofthe two cover sheets, the personalization data are inscribed with alaser beam. To impede the reproduction of such identification cards withmodern copiers, the personalization data are often introduced intometallic layers in front of a dark background. Since the metallicsubstrate causes a specular reflection of incident light beams, and thedetector in copiers is usually disposed such that it can pick up onlythe diffusely scattered light from the original, the metallic surfacesand the introduced data appear all black in the copy.

Despite the recognized high security level of laser-personalizedidentification cards, there is a residual risk of forgery as a result ofa separation of card front and card back and the resulting possiblemanipulation of the information located inside, such as text and imageobjects. In particular, after a separation of the card sheets, a metalfoil located inside is counterfeitable or replaceable.

Based on that, the object of the present invention is to specify a datacarrier of the kind described above having increased counterfeitsecurity. Furthermore, it should be possible, preferably also forlaypersons, to detect manipulation attempts with simple means.

This object is solved by the data carrier having the features of themain claim. A method for manufacturing such a data carrier and a methodfor checking the integrity of such data carriers are specified in thecoordinated claims. Developments of the present invention are thesubject of the dependent claims.

The data carrier according to the present invention builds on the stateof the art in that it comprises a laser-sensitive layer that is opaquein the visible spectral range and that is combined with a securing layerthat is metallized at least in a sub-area. Said identifiers areintroduced by the laser beam simultaneously and in “perfect register”into the laser-sensitive layer and the metallized sub-area of thesecuring layer. In this way, the integrity of the data carrier can bechecked at any time by checking the register accuracy of theidentifiers. For this, a very luminous flashlight or even viewing thedata carrier against daylight is sufficient.

Advantageously, the introduction of the identifiers into the securinglayer can occur, for example, through material ablation in themetallized sub-area or through a local transformation of the metal intoa transparent or translucent modification.

In expedient embodiments, one or more intermediate layers are disposedbetween the laser-sensitive layer and the securing layer. Theintermediate layers are preferably transparent and can also be coloredand/or printed on. They can also be furnished with fluorescentproperties. In particular, if the intermediate layers are notcontinuously transparent, they advantageously exhibit one or moreapertures in the area of the identifiers to enable the identifiers to beseen and to use the opaque background as a contrast element.

Advantageously, the metallized sub-area can be vapor deposited on thesecuring layer or formed by a printing layer of a metallic effect ink.The metallized sub-area can also exhibit a diffraction pattern,especially a hologram pattern, such that an additional angle-dependentimage impression is created for the viewer.

The laser-sensitive layer is preferably formed by a plastic foil that isdoped at least in a sub-area. In other, likewise advantageousembodiments, the laser-sensitive layer is formed by a plastic foil thatis provided at least in a sub-area with a printing layer that absorbsthe laser radiation. The plastic foil can then be transparent, as theopacity required for the contrast effect is provided by the printinglayer. Furthermore, the plastic foil can be furnished with fluorescentproperties, for example by incorporating fluorescent pigments duringmanufacturing of the foil. In both variants, the plastic foil can becomposed of, for example, polycarbonate or polyester. It is alsoconceivable to use paper as the laser-sensitive layer. Preferably, papermade of cotton fibers is used. The laser-sensitive layer can also be ametal layer. Preferably, the metallized sub-area and the laser-sensitivelayer are then formed of differently colored metals.

While only a single laser-sensitive layer that is opaque in the visiblespectral range has been described so far, according to the presentinvention, it is also possible to provide multiple such layers in thedata carrier. The various laser-sensitive layers can then be providedwith different types of identifiers or combined with different metallayers.

The identifiers introduced into the data carrier can include anypatterns or characters. Identifiers that comprise a halftone patternreproduced from an original, especially an image, such as a portrait,are particularly well suited, as the human eye can perceive even thesmallest discrepancies in congruence there. The halftone pattern ispreferably introduced in screening technique, different brightnesslevels of the halftone pattern being produced especially by a differentgrid-point density, a different grid-point size and/or by a differentgrid-point blackening.

In an advantageous development of the present invention, the metallizedsub-area, together with the opaque layer, displays, in impinging light,a tilt effect in which the image impression of the introducedidentifiers switches from a positive image to a negative image when theviewing angle changes. As explained in detail below, this contrastreversal is explained by the interplay of the specularly reflectingmetallic sub-areas and the diffusely scattering identifier areas. Thiseffect can also be used as copy protection.

Instead of a single metallized securing layer, multiple such securinglayers can also be provided. For example, a spatial effect can beachieved by combining metallized securing layers in different levels.The metallized securing layers can additionally be provided with a lasertilt image pattern, as described for example in publication EP 0219 012A2.

For protection, the laser-sensitive layer and/or the securing layer canbe covered with further layers that are transparent at least in the areaof the identifiers, such that the laser-sensitive layer or the securinglayer, preferably both layers, are disposed in the interior of the datacarrier.

The data carrier preferably constitutes an identification card, such asa credit card, bank card, cash card, authorization card, identity cardor passport personalization page. The data carrier can also constitute atransfer element disposed on a carrier layer for application to anidentification card or the like.

To manufacture a described data carrier, the laser-sensitive layer thatis opaque in the visible spectral range is combined with the securinglayer that is metallized at least in a sub-area and, where appropriate,with further layers, and, for introducing the identifiers, the layerstructure is impinged on from the side of the laser-sensitive layer withlaser radiation, causing the identifiers to be introduced simultaneouslyand in “perfect register” into the laser-sensitive layer and themetallized sub-area of the securing layer. The laser beam preferablyimpinges vertically on the layer structure. However, any other angle ofincidence of the laser beam on the layer structure is also conceivable.Thus, if the laser beam is radiated at a certain angle, e.g. 70°, to thecard surface, the congruence of the engraved identifiers in thedifferent levels of the layer structure is, in principle, preserved.When viewing, the congruence must then, of course, be checked at theangle at which the identifier was engraved in the layer structure bymeans of a laser.

The identifiers are preferably introduced with pulsed laser radiation,preferably having a wavelength in the infrared or visible spectralrange. Advantageously, a halftone pattern reproduced in screeningtechnique from an original is used as an identifier, differentbrightness levels of the halftone pattern being produced especially by adifferent grid-point density, a different grid-point size and/or by adifferent grid-point blackening. Said grid-point density is expedientlyselected to be between 50 and 500 dpi (dots per inch), preferablybetween 150 and 250 dpi, particularly preferably between 170 and 200dpi.

To check the integrity of a data carrier of the kind described, the datacarrier is illuminated with a strong light source, the register accuracyof the identifiers in the opaque, laser-sensitive layer and themetallized sub-area of the securing layer is determined, and on thebasis of the determined register accuracy, the integrity of the datacarrier is assessed.

Overall, the present invention provides a significant increase in thesecurity of personalized data carriers, and at the same time, simpleverifiability of the protection is given. When manufacturing cards, forexample, three pieces of information for protecting against forgery canbe introduced into the card material in one work step withoutsubstantial impact on the throughput:

-   1) a photo, for example on the front of the card,-   2) a transmitted light effect that delivers, depending on the kind    of personalization, a positive or negative image, and-   3) a personalization of a metallized foil layer, opposite and    absolutely congruent to the photo on the front of the card.

Further exemplary embodiments and advantages of the present inventionare explained below by reference to the drawings. To improve clarity, adepiction to scale and proportion was dispensed with in the drawings.

Shown are:

FIG. 1 the front view of an identification card according to anexemplary embodiment of the present invention, diagrammed schematically,

FIG. 2 the rear view of the identification card in FIG. 1,

FIG. 3 a cross section through the identification card in FIG. 1 alongthe line III-III,

FIG. 4 to 7 cross-sectional views of further identification cardsaccording to exemplary embodiments of the present invention.

FIG. 1 and 2 show the front and rear view of an identification card 10according to the present invention, diagrammed schematically. Theidentification card 10 includes a portrait 12 of the cardholder, as wellas further personal data 14, in the exemplary embodiment the first andlast name of the holder. Furthermore, the identification card caninclude further personal or non-personal data 16, such as birth date,nationality, issuing authority, issue date and the like. The portrait 12and the name 14 on the identification card 10 are for illustrationpurposes only and do not correspond to any real person.

While the front 26 of the identification card 10 displays the portraitof the cardholder as a screened halftone image 12, from the card back28, a portion of the portrait is visible in a metal foil 18. Due totheir creation simultaneously and in substantially accurate register (or“perfect register” as that term is used in the art), described below, inan intact identification card 10, the halftone portrait 12 and theportrait inscribed in the metal foil 18 are disposed completelycongruently.

This congruence can be checked with simple aids, for example with astrong flashlight or even by viewing the identification card againstdaylight. In a manipulation attempt through separation of the card foilsand replacement or forgery of the metal foil 18 located inside, thecongruence of the two portraits is destroyed and can then no longer bereconstructed with the original accuracy. The personalization of thecard front and the metal foil located inside is thus protectedeffectively and easily verifiably.

The layer structure of the identification card 10 and its manufacturewill now be described with reference to the simplified schematic diagramin FIG. 3. In the simplest case, the identification card 10 is composedof a core layer 20 that is opaque in the visible spectral range, and atransparent foil 22 on which is vapor deposited, in a sub-area, a metallayer 24, for example an aluminum, copper or gold layer.

For personalization, the identification card 10 is impinged on from thecard front 26 with pulsed, infrared laser radiation. For this, the corelayer 20 is doped with additives that are capable of absorbing theinfrared laser radiation and effecting a local blackening 30 of the corelayer 20. The additives are, for example, fillers. It is possible tocontrol the absorption of the laser light and thus the degree ofblackening depending on the kind of filler and/or the filler content.The pulse energy of the laser radiation is selected such that itpenetrates the core layer 20 and is absorbed in the metal layer 24.Through the influence of the laser radiation, the optical properties ofthe thin metal layer 24 in the captured modification areas 32 arechanged locally such that the portrait inscribed from the front isvisible mirror reversed when viewed from the card back 28. The change ofstate of the metal layer 24 can, for example, consist in a partial orcomplete local ablation of the metal layer or in a local transformationof the metal layer into a transparent or translucent modification.

In the exemplary embodiment, a Nd:YAG laser having a wavelength of 1.064μm, a beam diameter of about 60 μm and a pulse energy of up to 2 J/cm²was used to introduce the identifiers. Other infrared lasers, such asNd:glass lasers or the longer-wave CO₂ lasers, are also possible for thepersonalization. It is understood that the laser parameters concretelyused in each case, such as beam diameter and pulse energy, are matchedto the number and the thickness of the layers to be engraved.

By scanning the image surface of the portrait 12 in a defined grid and apulse-to-pulse variation of the laser output corresponding in each caseto the blackening level, a halftone image like the portrait 12 having aresolution of, for example, 200 dpi can easily be produced.

Through suitable selection of the background of the metal layer 24, itis possible to achieve a tilt effect when viewed from the card back 28.Here, the image impression tilts in reflected light when the viewingangle changes, independently of the angle of tilt, from a positive imageto a negative image. Without being bound to a specific explanation, thecontrast reversal is explained by the fact that light incident from theback is specularly reflected by the unmodified areas of the metal layer24, while it scatters diffusely in the ablated or modified areas 32. Ifthe viewer is located in the solid angle of the specular reflection,then the metal layer 24 appears brighter to him than the modified areas32, while from other viewing angles, the diffusely reflecting area 32appears to him to be unchanged in brightness, but the metal layer areasappear dark. This effect is particularly noticeable when the metal layer24 is disposed in front of a light, for example white or pastel-colored,background.

FIG. 4 shows a further exemplary embodiment of an inventiveidentification card 40 having a more complex layer structure. The layersequence of the identification card 40 comprises a transparent lightlydoped foil 42, a transparent undoped foil 44, a transparent heavilydoped foil 46, an opaque foil 48, a transparent undoped foil 50 and atransparent lightly doped foil 52. In the exemplary embodiment, all ofthe cited foils are polycarbonate foils. If appropriate, the foils arefurnished with fluorescent properties.

Prior to joining the foils, a metal layer 54, here an aluminum layer, ofseveral tenths of a μm thickness was vapor deposited on the transparentundoped foil 50. The foils were then laminated and the card thus formed,as described above, was personalized by laser engraving. Thereby, localblackenings 56 were created in the doped foils 42 and 46 due to theabsorption of the laser radiation. At the same time, due to the laserradiation in the modification areas 58, the optical properties of themetal layer 54 were irreversibly changed locally and congruently withthe blackenings 56. Further identifiers can be inscribed in the dopedfoil 52 from the back of the identification card 40.

For the purposes of clear illustration, the exemplary embodiment in FIG.5 is shown in an exploded view in which the individual layers have notyet been joined and in which the personalization of the identificationcard 60 has not yet occurred. The layer structure of the identificationcard 60 comprises a transparent lightly doped foil 62, a printed-ontransparent foil 64 that can be undoped or lightly doped, a heavilydoped transparent foil 68 that is provided with a thin metal layer 76, aprinted-on heavily doped transparent foil 70 and a lightly dopedtransparent foil 74. In this exemplary embodiment, too, the cited foilsare polycarbonate foils. Here, too, the foils can be furnished withfluorescent properties.

The foils 64 and 70 are each provided with a printing layer, 66 and 72,the printing layer 72 exhibiting, in the area of the metal layer 76 orat least in the area of the introduced identifiers, apertures 80 toenable the identifiers to be seen. In this exemplary embodiment, theopacity of the card body is achieved, not through an opaque foil, butrather through the printing layers 66 and 72 that are opaque at least insub-areas. In particular, the printing layer 66 is opaque in the area ofthe metal layer 76. The printing layers 66 and/or 72 can also be appliedwith effect inks, such as fluorescent inks or inks containing opticallyvariable pigments.

In the exemplary embodiment, the metal layer 76 is formed by a hologrampatch having a diffraction pattern 78 that, in a manner that is knownper se, gives the viewer, in addition to the above-described portrait,an angle-dependent image impression. The hologram patch can include, forexample, an angle-dependent color play or an image motif that moves orchanges when tilted. Such a hologram patch can, of course, be used inall of the embodiments described instead of a simple metal layer.

FIG. 6 shows a further exemplary embodiment of an identification cardaccording to the present invention. The layer sequence of the cardcomprises a transparent foil 90 that was printed on across its entiresurface with a fluorescent imprint 91. Above that is located a metalliclayer, preferably silver or gold colored 92. This is covered with atransparent foil 93 on which, in turn, a metallic layer 94 is locatedthat is preferably silver or gold colored. The metal layers 94 and 92preferably have a differently metallic appearance, such that the card,viewed from the top and the bottom, respectively, exhibits a differentappearance. This card structure is now impinged on from the side of thelayer 94 with laser radiation, such that the marking 100 is produced inthe layers 92 and 94. In this case, the marking is a metal ablation,such that apertures are created in the metal layer. By illuminating thecard from the side of the layer 90 with UV radiation, to a viewerviewing the card from the side of the coating 94, fluorescent patchesare perceptible in the area of the aperture 100. The apertures 100 thatappear fluorescent to the viewer when illuminated appropriately can bepictographic illustrations as well as codes.

FIG. 7 shows a further exemplary embodiment according to the presentinvention. The layers 95 are metallic layers that were vapor depositedon a transparent foil 97. The layers 96 are likewise metallic layersthat were vapor deposited on the side opposite the metallic layer 95.These two layer structures were each laminated onto one side of a foil98 doped with a fluorescent pigment. When this structure is impinged onwith laser radiation, the markings 101 are produced in the metal layer.By removing the corresponding metal layer on the patches 101, the viewercan again perceive, given appropriate illumination with excitingradiation, fluorescent marks on the patches 101.

1. A data carrier into which, by means of a laser beam, identifiers areintroduced that are visible in the form of irreversible changes, causedby the laser beam, in the optical properties of the data carrier,characterized in that: the data carrier comprises a laser-sensitivelayer that is opaque in the visible spectral range and that is combinedin such a way with a securing layer that is metallized at least in asub-area that the two layers overlap at the metallized sub-area of thesecuring layer, and the opaque, laser-sensitive layer and the securinglayer each include separate identifiers, the identifiers beingintroduced by the laser beam simultaneously and in register into theopaque, laser-sensitive layer and the metallized sub-area of thesecuring layer.
 2. The data carrier according to claim 1, characterizedin that the introduction of the identifiers into the securing layeroccurs through material ablation in the metallized sub-area.
 3. The datacarrier according to claim 1, characterized in that the introduction ofthe identifiers into the securing layer occurs through a localtransformation of the metal into a transparent or translucentmodification.
 4. The data carrier according to claim 1, characterized inthat one or more intermediate layers are disposed between thelaser-sensitive layer and the securing layer.
 5. The data carrieraccording to claim 4, characterized in that the intermediate layer(s)are colored and/or printed on and/or fluoresce.
 6. The data carrieraccording to claim 4, characterized in that the intermediate layer(s)exhibit one or more apertures in the area of the identifiers.
 7. Thedata carrier according to claim 1, characterized in that the metallizedsub-area is vapor deposited on the securing layer.
 8. The data carrieraccording to claim 1, characterized in that the metallized sub-area isformed by a printing layer of a metallic effect ink.
 9. The data carrieraccording to claim 1, characterized in that the metallized sub-areaexhibits a diffraction pattern.
 10. The data carrier according to claim1, characterized in that the laser-sensitive layer is formed by aplastic foil that is doped at least in a sub-area.
 11. The data carrieraccording to claim 1, characterized in that the laser-sensitive layer isformed by a plastic foil that is provided, at least in a sub-area, witha printing layer that absorbs the laser radiation.
 12. The data carrieraccording to claim 1, characterized in that multiple laser-sensitivelayers are provided that are opaque in the visible spectral range. 13.The data carrier according to claim 1, characterized in that theidentifiers comprise a halftone pattern reproduced from an original. 14.The data carrier according to claim 13, characterized in that thehalftone pattern is introduced in a screening technique, differentbrightness levels of the halftone pattern being produced by a differentgrid-point density, a different grid-point size and/or by a differentgrid-point blackening.
 15. The data carrier according to claim 1,characterized in that the metallized sub-area, together with the opaquelayer, displays, in reflected light, a tilt effect in which the imageimpression of the introduced identifiers switches from a positive imageto a negative image when the viewing angle changes.
 16. The data carrieraccording to claim 1, characterized in that multiple securing layers areprovided that are metallized at least in a sub-area, whereby thecombination of metallized securing layers in various levels achieves aspatial effect.
 17. The data carrier according to claim 1, characterizedin that the or one of the metallized securing layers is additionallyprovided with a laser-tilt-image pattern.
 18. The data carrier accordingto claim 1, characterized in that the laser-sensitive layer and/or thesecuring layer are covered with further layers that are transparent atleast in the area of the identifiers, such that at least one of thelaser-sensitive layer or the securing layer are disposed in the interiorof the data carrier.
 19. The data carrier according to claim 1,characterized in that the data carrier constitutes an identificationcard, such as a credit card, bank card, cash card, authorization card,identity card or passport personalization page.
 20. The data carrieraccording to claim 1, characterized in that the data carrier constitutesa transfer element disposed on a carrier layer for application to anidentification card or the like.
 21. A method for manufacturing a datacarrier according to claim 1, in which the laser-sensitive layer that isopaque in the visible spectral range is combined in such a way with thesecuring layer that is metallized at least in a sub-area that theopaque, laser-sensitive layer and the securing layer overlap at themetallized sub-area of the securing layer, and in which, to introducethe identifiers, the layer structure is impinged on from the side of thelaser-sensitive layer with laser radiation, causing separate identifiersto each be introduced simultaneously and in perfect register into thelaser-sensitive layer and the metallized sub-area of the securing layer.22. The method according to claim 21, characterized in that theidentifiers are introduced with pulsed laser radiation.
 23. The methodaccording to claim 21, characterized in that, as the identifier, ahalftone pattern reproduced from an original in a screening technique isintroduced, different brightness levels of the halftone pattern beingproduced by a different grid-point density, a different grid-point sizeand/or by a different grid-point blackening, and the grid-point densitybeing selected to be between 50 and 500 dpi.
 24. A method for checkingthe integrity of a data carrier according to claim 1, in which the datacarrier is illuminated with a strong light source, the register accuracyof the identifiers in the opaque, laser-sensitive layer and themetallized sub-area of the securing layer is determined, and on thebasis of the determined register accuracy, the integrity of the datacarrier is assessed.